Thread control device for sewing machines



June 26, 1962 w. KASTRUP THREAD CONTROL DEVICE FOR SEWING MACHINES 2 Sheets-Sheet 1 Filed March 6, 1961 INVENTUI? Wc-KN K KA STR u P June 26, 1962 w. KASTRUP THREAD CONTROL DEVICE FOR SEWING MACHINES 2 Sheets-Sheet 2 Filed March 6, 1961 ovnsvra Wemve R KA-sTRuP United States Patent T 3,045,681 THREAD CGNTROL DEVKIE FOR SEWING MACHINES Werner Kastrup, Heidsiekerheide uber Bielefeld, Germany, assignor to Durkoppwerke Aktiengesellschaft, Bielefeld, Germany, a German company Filed Mar. 6, 1961, Ser. No. 93,465 8 Claims. (Ci. 112-218) This invention relates to a device for the control of the needle thread in the formation of the thread loops for the loop-taker.

In the embroidering of the edges of a material in the manufacture of ornamental-shell edges and like work by means of zig-zag sewing machines, the needle penetrates alternately through the workpiece material on the one hand and past the edge of the workpiece on the other hand. Hereby there is always the possibility of thread breakage, in particular when the sewing machine is to be driven at high speed. A thread breakage is always unavoidable if, when the upward moving needle has formed the usual thread loop for seizing by the point of the looptaker, a second thread loop is formed from the excess length of thread between the thread supply and the needle eye and likewise lies in the path of movement of the point of the loop-taker.

This undesired loop formation in the vicinity of the loop-taker is particularly present when the needle stitches out of the workpiece. In this case, the thread loosened from the thread take-up, since it undergoes no tensioning due to friction against the workpiece, can form a second thread loop below the needle plate, which loop, when seized by the loop-taker, leads to thread breakage.

For the purpose of preventing thread breakage, a thread guide has already been proposed which is arranged on the needle clamp on the needle bar in order by deflection of the thread thereon, to prevent the loosened needle thread on its way between the needle eye and the thread take-up forming a second loop in the vicinity of the needle. This known thread guide solves the problem only inadequately, as it is uncontrolled and therefore is in operation in both directions of movement of the needle bar. The loosening of the thread caused by the thread take-up at the critical moment cannot be obviated so that, furthermore, there remains the possibility of a further running of the thread through the thread guide to the needle. Furthermore, with this known thread guide, there results an additional friction on the needle thread due to the deflection by said guide being continuous, which is undesirable in high-speed sewing machines.

The main object of the present invention is to provide an apparatus for the control of the needle thread when forming the thread loop for the loop-taker which prevents with certainty the above-mentioned undesired second loop formation.

The invention aims furthermore at providing a device for this purpose which is simple in construction and which can be applied without trouble to existing sewing machines.

The thread control device according to this invention is characterised by a thread deflection member moving with the needle bar and automatically controlled by its mass inertia moment to form a deflection loop in the thread as the needle bar begins its upward movement and to release the thread as the needle bar begins its downward movement.

In the preferred arrangements the thread deflector; which may be a wire stirrup formed substantially U- shaped, is pivotally mounted on the needle clamp and moves past a guide hole in such clamp through which the thread goes to the needle.

H 3,040,681 Patented June 26, 1962 The invention will now be described as to one embodiment, with reference to the accompanying drawings, wherein:

FIG. 1 is a perspective view of the lower end of a needle bar with the deflecting member in the position occupied during upward movement of the needle bar;

FIG. 2 is a side view to a smaller scale, showing the position of the deflecting member when the needle bar is moved downwards;

FIG. 3 is a' vertical section through the stitch-forming tool and the needle plate shortly before the entry of the loop-taker point into a satisfactorily-formed thread loop;

FIG. 4 is a vertical FIG. 3; and

FIGS. 5 and 6 show the possibilities of faulty loop formation without the use of the device according to this invention, when carrying out raised stitches by the needle.

On the needle bar 1 (FIGS. 1 and 2), there is located a needle clamp 2 for the fixing of a needle 3 by means of a clamp screw 4. A U-shaped bent wire stirrup 5 is rotatably mounted in the openings 6 of the needle clamp 2 by its two inwardly-turned ends of its arms. The wire stirrup 5 may be supported by its two arms resting on two projections 7 extending laterally from the needle clamp 2. The extent of upward deflection of the wire stirrup 5 is limited by its contact on the raised end face of the needle clamp 2.

A bore 8 running obliquely to the axis of the needle bar 1 serves for the guiding of the needle thread 9 which, coming from a thread take-up (not shown) above, the wire stirrup 5, is led through the bore 8 to the needle eye 10. The needle 3, after its passage through the stitch hole 12 in the needle plate 11 (FIGS. 3-6), co-operates with a double circular taker 13.

As illustrated in FIGS. 3 and 4, the needle 3 allows a loop 14 to be thrown out for seizing by the loop-taker point 15 as soon as the needle begins to move upwards. As shown, the friction occurring between the thread 9 and the workpiece 16 prevents the upward passage of the excess length of thread, at which point the loosening of the needle thread by the take-up means for the enlargement of the needle thread loop after the loop-taker point has entered it, has already commenced.

If, however, the needle 3 does not go through the workpiece, in the carrying out of so called raised stitches, for example when embroidering the workpiece edges by means of a zig-zag stitching, there is the possibility that the excess needle thread 9 released by the thread takeup can come unhindered through the stitch hole 12 and through the needle eye 10 and now form an enlarged loop 17 as illustrated in FIG. 5, which loop in this case can still be seized by the loop-taker point 15. Frequently, however, the case shown in FIG. 6 occurs in that a second loop 18 is formed between the needle plate 11 and the needle eye 10 which becomes placed around the needle 3 and is now seized by the loop-taker together with the loop 14, whereby a thread breakage results.

The device according to the invention aims at a satisfactory formation of thread loops for the loop-taker as shown in FIGS. 3 and 4, when carrying out raised stitches. This is attained in that, upon the upward movement of the needle bar 1 the wire stirrup 5 serving as a thread deflecting member is caused by its mass inertia to come automatically against the two lower stops 7 on the needle clamp 2, whereby the excess length of thread located between the thread take-up and the needle eye, in consequence of such deflection, is formed positively into a loop 19 (FIG. 1) located outside the stitch-forming tools. Upon downwards movement of the needle bar 1, the wire stirrup 5, likewise under the action of its mass section on the line IV-IV of a 3 inertia, contacts the raised endface of the needle clamp 2 (FIG. 2), whereby the deflection of the needle thread 9 ceases and also no additional friction on the thread can take place by the wire stirrup 5. What I claim is:

1. In a'sewing machine having a rising and falling needle bar, a needle plate and a loop taker beneath the needle plate, guide means on said needle bar for the thread going to the needle, and a thread deflecting member supported by the needle bar for free movement in one direction past said guide means, on upward movement of the bar to deflect the'thread into a loop and tor free movement in the opposite direction on downward movement of the bar to relieve the thread, and a mounting on the needle bar for said thread deflecting means allowing it to effect said movements under the influence of mass inertia in response to the rising and falling movements of the needle bar.

2. In a sewing machine having a rising and falling needle bar, a needle plate and a loop-taker beneath the needle plate, aneedle clamp on said needle bar, an inclined passageway in said needle clamp open to the front and bottom thereof to guide thread going to the needle, a thread-deflecting member pivotally mounted in said needle clamp and freely movable past the front opening of said passageway, in one direction to deflect the thread into a loop and in the other direction to relieve the thread, the pivot mounting of said thread deflector allowing it to efiect said movements under the influence of mass inertia in response to the rising and falling movements of the needle bar.

3. A sewing machine as claimed incl-aim 2, having ste means on said needle clamp to limit the pivotal movements of said thread-deflecting member.

4. A sewing machine :as claimed in claim 2, wherein said thread deflecting member is a wire stirrup having a cross bar lying in front of the needle clamp side arms lying alongside the needle clamp and inturned ends pivoted in the side parts of the needle clamp.

5. A sewing machine as claimed in claim 2, wherein said thread-deflecting member is a wire stirrup having a cross bar lying in front of the needle clamp, side arms lying alongside the needle clamp and inturned ends pivoted in the side parts of the needle clamp and having first stop means on the front of the needle clamp to limit the upwards pivoting movement of the stirrup, and further stop means on the sides of the needle clamp to limit the downwards movement of the stirrup.

6. In a sewing machine including a needle bar and needle clamp, a device for the control of a needle thread in the formation of thread loops for the looptaker, characterized by a thread deflection member supported by and moving relative to the needle bar and automatically caused by its inertia to form a deflection loop in the thread as the needle bar is accelerating upwards and to relieve the thread as the needle bar is accelerating downwards.

7. The invention as claimed in claim 6, wherein the said deflection member is pivotally attached to the needle clamp and moves past a guide hole in the clamp through which the thread goes to the needle. 8. The invention as claimed in claim 6, characterized in that the clamp has a guide hole through which the thread goes to me-needle and the thread deflection member moves past said guide hole and comprises a wire thread stirrup formed substantially U-shaped and is pivotally attached to the'needle clamp, the needle clamp carrying a lateral projection and which Wire stirrup as the needle bar accelerates upwards, lies on said clamp carrying projection going to its inertia, whereby the excess lengthofrthread located between the thread take-up and the needle eye, in consequence of the deflection, is for-med into a loop and, as the needle bar accelerates downwards, such stirrup swings upward and contacts the needle clamp above said guide hole whereby the deflection of the needle thread into the said loop ceases.

References Cited in the file of this patent UNITED STATES PATENTS 

